1. Field of the Invention
The present invention relates generally to hydrocarbon base cementitious drilling fluids and methods, and more particularly, to hydrocarbon base drilling fluids which are selectively convertible to cementitious compositions that set into hard substantially impermeable masses.
2. Description of the Prior Art
A variety of drilling fluids are used in drilling well bores by the rotary drilling method. The most commonly utilized such drilling fluids are solids containing water base gels. However, when the well bores to be drilled penetrate water sensitive formations, hydrocarbon base drilling fluids are utilized.
After a well bore is drilled during which the drilling fluid used is circulated through the well bore, the circulation of the drilling fluid is stopped and the well is usually logged after which a string of pipe, e.g., casing, is run into the well bore. The drilling fluid is cleaned up by circulating it downwardly through the interior of the pipe and upwardly through the annulus between the exterior of the pipe and the walls of the well bore while removing drilling solids and gas therefrom. Primary cementing operations are then performed in the well bore, i.e., the string of pipe disposed in the well bore is cemented therein by placing a cementing composition in the annulus between the pipe and the walls of the well bore. The cementing composition sets into a hard substantially impermeable mass whereby the pipe is bonded to the walls of the well bore and the annulus is sealed. When the cementing composition is run down the pipe and into the annulus, the drilling fluid in the pipe and annulus is displaced therefrom. The used drilling fluid is generally accumulated in a pit or tank and then disposed of.
The disposal of drilling fluid is time consuming and expensive, particularly in offshore drilling locations. In recent years, the expense has increased significantly in that drilling fluid often must be disposed of as a fluid which is hazardous to the environment. Thus, any environmentally safe use to which all or part of the drilling fluid can be put at a well site is highly advantageous in that it eliminates the need for subsequently disposing of all or part of the drilling fluid.
By the present invention, hydrocarbon base drilling fluids and methods of drilling well bores utilizing the drilling fluids and subsequently disposing of the drilling fluids by converting them to cementitious compositions are provided. The converted cementitious drilling fluid compositions can be used for carrying out cementing operations in the well bore, and any remaining portion thereof can be placed in an environmentally safe location wherein the drilling fluid composition sets into a hard cementitious mass.